M923A2 Fuel Filters, Draining and Priming.

[allpredatorcalls]

M923A2 Fuel Filters, Draining and Priming.


Okay I dusted out the ole M939 series maintenance manual (TM 9-2320-272-10, Jul 2012 Pub date) to familiarize myself with the fuel system. I decided since I have no idea when the filter bowls had been checked for water and or sediment, I would do that.


The manual is somewhat confusing / poorly written and shows illustrations that are not reflective of the configuration of my M923A2 with a 6CTA 8.3L turbo motor


I have a few questions for you guys with more expirence.

1. I have the driver’s side fuel filter assembly. The maintenance manual WP0119-6 step a and b says it requires daily draining.
Does anyone do this that often? What’s a more realistic schedule?






2. The maintenance manual WP0119-6 step b. says open the inlet drain valve (fig 5 item 1) my filter doesn’t have the valve. I did open the drain valve at the bottom of the filter bowl (fig 5 item 3)and it just sucked air for 4 or 5 seconds, so I turned it closed not wanting to induce a bunch of air into the system, it never drained fuel.
So what is the proper way to drain / check for water in the filter bowl on the wheel well filter? Let it suck air and eventually it will start draining fuel?


3. Regarding the engine mounted fuel/water separator the maintenance manual WP0119-6 step c says open the drain valve, drain into a container, and when done prime the fuel system. WP0119-6 step 2 lists the steps for priming the fuel system. The steps (b and c) refer you to the open air purge valve and a hand primer pup (fig 6 item 2) of which neither are installed on my truck in the position depicted in figure 6…. So what gives? How are you purging the air from the system.






4. I looked further into the maintenance manual TM-9-2320-272-23-2 WP0239-2 (priming fuel) which depicts my fuel transfer pump configuration. Based on the paint on the vent screw, and its location, I would guess it hasn’t been opened / purged since it was painted in overhaul back in 2009…
- So is the fuel/water separator drain another one of those things that is supposed to be done daily that never gets accomplished? Does anyone do this that often? What’s a more realistic schedule?
- What technique / procedure have you that have similarly configured fuel systems been using to purge air after checking for water or replacing fuel filters?

Thanks for your help

 

[mkcoen]

A lot of the 923A2s had the large filter removed. If you look at the TM for the A2 it doesn't show the large filter. Mine had no filter at all and the petcock was so full of blasting media from the overhaul that it wouldn't open. I pulled the petcock, cleaned it out, and went ahead and added the filter back in. Better too many filters than not enough.

 

[74M35A2]

My large filter sucks air when trying to drain also. There is a Schrader vent valve on top of the large filter, and as soon as you press this in, it allows the canister to drain.

On the engine mounted filter, your procedure is correct, or at least how I do it. Open drain, wait about 30 seconds, then filter will drain.

 

[allpredatorcalls]

Thanks, where are you venting the air from the system (which fitting/bleed port are you loosing.. picture?).. Can you use the same schrader valve and pressurize the lower larger fuel filter with a shop air hose and push fuel (and any air in the system/bubbles) through both the large and small fuel filters to the bleed port?

Thanks,

AP

 

[Doug Roberts]

Daily , maybe more than what is needed , but keeping the tank as full as possible ( leave the expansion though ) will reduce water in your fuel . To me it sounds like your filter needs to be changed out yesterday

 

[Csm Davis]

A lot of the 923A2s had the large filter removed. If you look at the TM for the A2 it doesn't show the large filter. Mine had no filter at all and the petcock was so full of blasting media from the overhaul that it wouldn't open. I pulled the petcock, cleaned it out, and went ahead and added the filter back in. Better too many filters than not enough.

Okay this first the a2s originally didn't have the large filter on the frame then the military made them start putting them on again and released a MWO to put them on the trucks that didn't have them.
As to draining the water I do mine after each fill up that way I know if I am getting good fuel. I would say each fill up or once a week will be fine, this is for the large canister.
If you have the small filter only or with the little inline filter I would check the water separator on the engine mounted filter everyday or every fill up which ever come first, and keep a spare inline filter in the truck or like me add the large canister or other large filter inline.

 

[Csm Davis]

Also not all had the petcocks or shader valves but should have one or both as it is needed to drain the canister n and you should always be sure they are clean as they will suck in dirt and always keep a metal cap with a seal in it on the shader valve, as they are not good at keeping air out.

 

[allpredatorcalls]

good info, thanks.

 

[z0sickkk]

Anyone know where the drain purge valve is on the A2 for the hand prime or near it?

Did fuel filters, pressurized tank, hand primed, cracked injectors, etc., still won't start.

My hand primer setup is identical to the ones posted, but different from the TM's listed for the A1.

Thanks.

 

[dilligaf13]

That's because you more than likely have a M939A2 which has a different motor than the A1.

 

[z0sickkk]

That's because you more than likely have a M939A2 which has a different motor than the A1.

Correct. The original poster has an A2. My hand prime setup looks identical to the pictures he posted, I just need to know where the "bleed purge valve" is. That's all. Apparently I cannot locate it online or on the truck.

 

[dilligaf13]

http://www.steelsoldiers.com/showth...-fuel-filter&p=1446778&highlight=#post1446778

 

[z0sickkk]

Thanks dilligaf13! That's what I needed

 

[dilligaf13]

No worries.

 

[Stonepicker1]

I have some of the large fuel filters listed in the classifieds.

http://www.steelsoldiers.com/showth...-ton-trucks-M939-M939A1-and-M818-M816-wrecker

When I was a Military tech, we would change these filters once a year. That Algae grows quickly in the tank when it just sits in the motor-pool.